1. Field of the Invention
The present invention relates to a method of manufacturing a liquid jet head which ejects liquid droplets for recording on a recording medium, and more particularly, to a method of manufacturing a liquid jet head in which ejection channels and dummy channels are alternately arranged in parallel with one another, a liquid jet head, and a liquid jet apparatus.
2. Description of the Related Art
In recent years, there has been used an ink jet type liquid jet head which ejects ink droplets onto recording paper and the like to draw letters and diagrams, or ejects a liquid material onto a surface of an element substrate to form a functional thin film. The liquid jet head of this type is supplied with ink or a liquid material from a liquid tank via a supply tube, and is caused to eject the ink or the liquid material filled in channels thereof from nozzles communicated to the channels. At the time of ink ejection, the liquid jet head and a recording medium for recording the jetted liquid are moved, to thereby record the letters and diagrams or form the functional thin film in a predetermined shape. As a liquid jet head of this kind, a liquid jet head of a share mode type is known. In such a liquid jet head of the share mode type, ejection channels and dummy channels are alternately formed in a surface of a piezoelectric substrate, and, by instantaneously deforming a partition wall between an ejection channel and a dummy channels, a liquid droplet is caused to be ejected from the ejection channel.
FIG. 8 illustrates a cross-sectional structure of an ink jet head described in Japanese Patent Application Laid-open No. 2000-168094. An ink jet head 100 includes a bottom wall 124 having ejection channels 112 and dummy channels 111 alternately formed therein and a top wall 110 disposed on an upper surface of the bottom wall 124. A piezoelectric side wall 103 is formed between an ejection channel 112 and a dummy channel 111. The piezoelectric side wall 103 includes an upper wall portion 125 which is an upper half thereof and a lower wall portion 126 which is a lower half thereof. The upper wall portion 125 is polarized in an upward direction while the lower wall portion 126 is polarized in a downward direction. Electrodes 105 are formed on wall surfaces of the respective piezoelectric side walls 103. Electrodes 1053 which are electrically connected to each other are formed on surfaces of the piezoelectric side walls 103 forming an ejection channel 112, while electrodes 105A which are electrically separated from each other are formed on surfaces of the piezoelectric side walls 103 forming a dummy channel 111. A nozzle plate (not shown) is disposed on a front surface of the ink jet head 100, and nozzles 116 for communicating with the ejection channels 112, respectively, are formed in the nozzle plate.
The ink jet head 100 is driven as follows. Voltage is applied between electrodes 105B disposed in an ejection channel 112 and electrodes 105A formed on side surfaces on the ejection channel 112 side of two dummy channels 111 positioned on both sides of the ejection channel 112. Then, piezoelectric thickness shear deformation is caused in the piezoelectric side walls 103 in directions of increasing the capacity of the ejection channel 112. After a predetermined length of time passes, the application of the voltage is stopped, the capacity of the ejection channel 112 changes from the increased state to a natural state, pressure is applied to ink in the ejection channel 112, and an ink droplet is ejected from the nozzle 116.
The ink jet head 100 is manufactured as follows. First, a piezoelectric ceramic layer which is polarized in the upward direction is adhered to another piezoelectric ceramic layer which is polarized in the downward direction to form an actuator substrate 102. Then, grooves in parallel with one another are formed in the actuator substrate 102 by cutting with a diamond cutter or the like to form the piezoelectric side walls 103 including the upper wall portions 125 and the lower wall portions 126. The electrodes 105A and 105B are formed by vacuum deposition or the like on side surfaces of the piezoelectric side walls 103 formed in this way. However, it is necessary to electrically separate the electrodes 105A on the piezoelectric side walls 103 of a dummy channel 111 for the purpose of being able to independently drive adjacent ejection channels 112. Therefore, using a laser or a diamond cutter from an opening side of the piezoelectric side wall 103, a separating groove 118 is formed in the electrode formed on a bottom surface of a dummy channel 111 to electrically separate the electrodes 105A on the right side wall and the left side wall.
However, it takes a great time to apply a laser beam into each of the dummy channels 111 or to insert a diamond cutter which is thinner than the width of the dummy channels 111 into each of the dummy channels 111 to cut the electrodes in forming the separating grooves 118. Further, as the pitch of the ejection channels 112 decreases and the dummy channels 111 become narrower, alignment of the laser beam or the diamond cutter becomes quite difficult. Still further, problems become obvious including that a laser beam does not reach the bottom surface of a dummy channel 111, that a laser beam is also applied to an upper surface of a piezoelectric side wall 103, and that the required thickness of the diamond cutter is too small to manufacture.